Presently, intravenous fluid therapy protocols suggest the use of an air eliminating filter (AEF) during the administration of fluids to a patient. Typically, an air eliminating filter includes a primary filtration media comprising a hydrophilic microporous membrane having pore sizes ranging from about 0.2 .mu.m to about 20.0 .mu.m, and a vent comprising a hydrophobic microporous membrane having pore sizes ranging from 0.02 .mu.m to 0.45.mu.m.
Ideally, during actual intravenous administration of prescribed fluids to a patient, an AEF should be located in a position wherein the AEF is disposed at a level equal to an infusion site of the patient. However, in actual practice, the AEF will often be located in a position that is higher than the infusion site. Prescribed fluid flow rates through an AEF can range from as little as 2 milliliters per hour to over 1 liter per hour. However, when low fluid flow rates are coupled with an AEF being located higher than the infusion site, an environment will be created which permits retrograde movement of prescribed fluids away from the patient.
When an AEF is located in a position that is higher than the infusion site of the patient, the AEF will develop a head pressure because the AEF is vented. This head pressure causes the free flow of fluids from the proximal chamber of the AEF, and therefore, causes the proximal chamber to empty. The proximal chamber will remain empty as long as the AEF is higher than the infusion site. This empty proximal chamber is the primary factor in contributing to the retrograde movement of prescribed fluids away from the patient.
Because most patients receiving intravenous therapy are either fully ambulatory, or are able to move about in their beds, the position of the AEF relative to the infusion site changes. Typically, such position changes result in the AEF going from a position higher than the infusion site, to a position that is lower than the infusion site. At this juncture, there is a negative pressure gradient formed between the patient and the AEF. Consequently, fluid in the intravenous tubing distal to the AEF, and body fluids from the patient, freely move in a retrograde manner up the intravenous tubing and away from the patient.
Retrograde movement of fluids can cause serious clinical situations to arise. More particularly, during retrograde movement of fluids, the patient does not receive prescribed intravenous fluids. Also, the retrograde movement of body fluids, in particular blood, can cause clots to form in the intravenous tubing distal to the AEF, or in the infusion catheter. If a clot is formed, costly procedures must be initiated to dissolve the clot, or the infusion must be discontinued. Such a discontinuation requires the removal of an infusion catheter, the location of a new infusion site, and the supply of a new AEF filter and support assembly. As may be appreciated, this results in higher medical costs and additional physical and mental trauma for the patient.
The foregoing illustrates limitations known to exist in present intravenous therapy techniques and assemblies. Thus, it is apparent that it would be advantageous to provide an improved apparatus and method directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.